Diamond and graphite are two well known allotropic forms of carbon. A new allotropic form, the fullerenes, has been prepared by graphite volatilization (see W. Kratschmer et al., Nature, 347, 354 (1990)).
Typically, fullerenes each have 12 pentagons, but differing numbers of hexagons. The pentagons are required in order to allow the curvature and eventual closure of the surface upon itself. The most abundant species of fullerenes identified to date is the C.sub.60 molecule or Buckminsterfullerene. C.sub.60 is a hollow molecule that consists of carbon atoms located at the vertices of 12 pentagons and 20 hexagons arranged to form an icosahedron. The inner hollow space of the fullerene (about 3.8 Angstroms in diameter) can accommodate any metal ion of the periodic table, thus suggesting that at least two isomers of any given fullerene-metal composition can exist: the metal may be inside (endohedral) or outside (exohedral) the fullerene cage. The second most abundant species classified to date is C.sub.70 and contains 12 pentagons and 25 hexagons. Fullerenes containing from 30 to many hundreds carbon atoms have detected by mass spectrometry. For further information concerning fullerenes, see, e.g., H. W. Kroto et al., Chemical Reviews, 91, 1213-1235 (1991).
As used in this application, the term "fullerenes" means hollow, all carbon-containing molecules having carbon atoms only in even numbers and located at the vertices of 12 pentagons (five membered carbon rings), but having differing numbers of hexagons (six membered carbon rings), and having the formula C.sub.2n where n is 10 or greater.
Ions of metal complexes of fullerenes have been observed in the gas phase by mass spectrometry (see J. R. Heath, et al. J. Am. Chem. Soc., 107, 7779 (1985), and D. M. Cox et al., J. Chem. Phys., 88( 3), 588 ( 988)).
Bausch et al., J. Am. Chem. Soc., 113, 3205-3206 (1991) discloses the synthesis of Li.sub.x C.sub.60 and Li.sub.x C.sub.70 salts in tetrahydrofuran ("THF"), but requires the use of ultrasound to effect the synthesis. Applicant's process is different from the foregoing in that it does not use ultrasound. Finally, Wang, et al., Inorg. Chem., 30, 2838-2839 (1991) discloses a process for making K.sub.x C.sub.60 by reacting potassium with a solution of C.sub.60 in toluene. The process of applicant's invention was made before the foregoing two publication dates.
The portion of the disclosure herein that relates to C.sub.60 fulleride salts having the formula A.sub.n (C.sub.x).sub.m wherein A is a monovalent metal cation, n is from +1 to +3 depending on the valence of C.sub.x and C.sub.x is a C.sub.60 fulleride anion (where m equals 1) having a valence of from -1 to -3 is the subject of copending application U.S. Ser. No. 798,390 filed Nov. 26, 1991.